The present invention relates to a synergistic mixture of hydrocarbon soluble or dispersible additives for oleaginous compositions such as lubricating oils, including power transmitting fluids and engine lubricating oils, and to the oleaginous compositions in which they are contained.
There are many instances, as is well known, particularly under boundary lubrication conditions where two moving surfaces in contact with each other must be lubricated, or otherwise protected, so as to prevent wear, and to insure continued movement. There are other instances where friction between two rubbing surfaces is sought to be modified but not necessarily minimized. By controlling friction between two surfaces, the power required to impart movement from one surface to another is also controlled.
For example, a specialized property sought to be imparted to certain lube oil compositions adapted for use as an automatic transmission fluid is the friction modification characteristic of the fluid. This property distinguishes automatic transmission fluids (ATF) from other lubricants, and in fact between types of ATFs as well. Such characteristic quality has received the most attention by both the transmission manufacturers and fluid producers for many years. This attention stems from the fact that the friction requirements of an ATF are unique and depend on the transmission and clutch design, as well as on the type of clutch plate material used.
Another property sought to be imparted to lubricating oil compositions including automatic transmission fluids is reduced wear such as bearing and power component wear.
As is also well known, both wear and friction modification can be controlled through the addition of suitable additives with varying degrees of success.
While there are many known additives which may be classified as anti-wear, or friction modifying agents, it is also known that many of these additives act in a different physical or chemical manner and often compete with one another, e.g. they may compete for the surface of the moving metal parts which are subjected to lubrication. Accordingly, extreme care must be exercised in the selection of these additives to insure compatibility and effectiveness.
The metal dihydrocarbyl dithiophosphates are one of the additives which are known to exhibit anti-oxidant and anti-wear properties. The most commonly used additives of this class are the zinc dialkyl dithiophosphates (ZDDP) which are conventionally used in lubricant compositions. While such zinc compounds afford excellent oxidation resistance and exhibit superior anti-wear properties, they can be corrosive.
Both anti-wear and friction modifying agents function by forming a coating on the surface of the moving metal parts. The coating bonds are generally effected physically and/or chemically. Consequently, if the bonding between the anti-wear agent and the metal part is stronger than the bonding between the friction modifying agent and the metal part, the anti-wear agent will displace the friction modifying agent at the metal surface, i.e. at the metal/fluid lubrication boundary interface. This results in a loss in the ability of the friction modifying agent to exert its intended effect.
Various tests have been designed by auto manufacturers for measuring ATF friction and anti-wear properties to evaluate the performance of additives in view of the requirements of particular transmission designs and their ability to impart transmission durability and smooth shifting under a variety of load conditions.
Friction modification is typically evaluated on an SAE No. 2 friction apparatus. In this test, the motor and flywheel of the friction machine (filled with fluid to be tested) are accelerated to constant speed, the motor is shut off and the flywheel speed is decreased to zero by application of the clutch. The clutch plates are then released, the flywheel is again accelerated to constant speed, and the clutch pack which is immersed in the test fluid is engaged again. This process is repeated many times with each clutch engagement being called a cycle.
During the clutch application, friction torque is recorded as a function of time. The friction data obtained are either the torque traces themselves or friction coefficients calculated from the torque traces. The shape of the torque trace desired is set by the auto manufacturers. One way of expressing this shape mathematically is to determine the torque: (a) when the flywheel speed is midway between the maximum constant speed selected and zero speed (such torque measurement is referred to herein as T.sub.D) and (b) when as the flywheel speed approaches zero rpm (such torque measurement is referred to herein as T.sub.O). Such torques can then be used to determine the torque ratio which is expressed as T.sub.O /T.sub.D, or alternatively, to determine the torque differential T.sub.O -T.sub.D. The typical optimum values for torque ratio and torque differential are set by the auto manufacturers. As the T.sub.O /T.sub.D increasingly exceeds 1, a transmission will typically exhibit shorter harsher shifts as it changes gears. On the other hand as T.sub.O /T.sub.D decreases below 1, there is an increasingly greater danger of clutch slippage when the transmission changes gears. Similar relationships exist with respect to a T.sub.O -T.sub.D target value of 0.
While many automatic transmission fluids can achieve target values of T.sub.O /T.sub.D after a minimum number of cycles, it becomes increasingly more difficult to sustain such target values as the number of cycles are increased. The ability of an ATF to sustain such desired friction properties is referred to herein as friction stability or durability A high level of friction stability is difficult to achieve with ATFs containing certain anti-wear additives. It is believed that as the ATF ages under the influence of the heat of friction, the anti-wear agent can break down and the decomposition products displace conventional friction modifiers at the metal/fluid lubrication boundary interface. As a result, the fluid may exhibit varying friction properties.
Attempts to improve friction stability by simply adding more friction modifier have not met with success because this tends to reduce the breakaway static torque (T.sub.S) of the fluid. This parameter when expressed as the breakaway static torque ratio (T.sub.S /T.sub.D) reflects the relative tendency of engaged parts, such as clutch packs, bands and drums, to slip under load. If this value is too low, the slippage can impair the driveability and safety of the vehicle.
Transmission designs have undergone radical changes, thereby necessitating the formulation of ATF additives capable of meeting new and more stringent property requirements needed to match such design changes.
No base oil alone can even approach the many special properties required for ATF service. Consequently, it is necessary to employ several chemical additives, each of which is designed to impart or improve a specific property of the fluid. Consequently, it becomes particularly advantageous when one additive can perform more than one function, thereby reducing the number of additives needed to be present in the formulation.
Accordingly, there has been a continuing search for new additives possessed of one or more properties which render them suitable for use in ATF compositions, as well as other oleaginous compositions. There also has been a search for new combinations of additives which not only provide ATF compositions, as well as other oleaginous compositions, with the various specific properties that are required, but which are compatible with each other in the sense that they do not exhibit any substantial tendency to compete with each other, nor to otherwise reduce the effectiveness of the various additives in the compositions. The present invention was developed in response to this search.
U.S. Pat. No. 3,034,907 discloses agents which are effective for hindering or retarding rust formation on iron surfaces and ice formation in the intake system of internal combustion engines. The agents which are disclosed are characterized by a content of (a) a hydrophobic organic carrier, (b) a carboxylic acid amide monocarboxylic acid, and (c) an at least equivalent amount of a hydroxyalkylated nitrogen base which contains at least one lipophilic radical. The hydroxyalkylated nitrogen base corresponds to the general formula ##STR2## wherein L represents a lipophilic radical; X represents a bridging member which is bound to the nitrogen atom by means of an aliphatic carbon atom and which is selected from lower --O-alkylene, --S-alkylene, --O-hydroxyalkylene, --S-hydroxyalkylene, ##STR3## (R'=H, alkyl, hydroxyalkyl), --CO--O-alkylene, and --CO--O-hydroxyalkylene radicals; n represents the integer 0 or 1; R.sub.1 represents hydrogen, a lower alkyl or lower hydroxyalkyl or lower aminoalkyl radical; and R.sub.2 is the same as (L-X.sub.n) and R.sub.1. In one embodiment, L represents an aliphatic C.sub.12 -C.sub.18 hydrocarbon radical, n is 0, and at least one of R.sub.1 and R.sub.2 is a low molecular weight hydroxyalkyl or hydroxyalkylaminoethyl radical.
U.S. Pat. No. 3,933,659 discloses lubricating oil position which comprise a major amount of an oil of lubricating viscosity, and an effective amount of each of the following: (1) an alkenyl succinimide, (2) a Group II metal salt of a dihydrocarbyl dithiophosphoric acid, (3) a compound selected from the group consisting of (a) fatty acid esters of dihydric and other polyhydric alcohols, and oil soluble oxyalkylated derivatives therof, (b) fatty acid amides of low molecular weight amino acids, (c) N-fatty alkyl-N,N-diethanol amines, (d) N-fatty alkyl-N,N-di(ethoxyethanol) amines, (e) N-fatty alkyl-N,N-dipoly(ethoxy) ethanol amines, and (f) mixtures thereof, and (4) a basic sulfurized alkaline earth metal alkyl phenate. Such lubricating compositions are useful as functional fluids in systems requiring fluid coupling, hydraulic fluid and/or lubrication of relatively moving parts, particularly as automatic transmission fluids.
U.S. Pat. No. 4,409,000 discloses the use of combinations of certain hydroxy amines, particularly the "Ethomeens", and hydrocarbon-soluble carboxylic dispersants as engine and carburetor detergents for normally liquid fuels.
U.S. Pat. No. 4,231,883 relates to the use of an alkoxylated hydrocarbyl amine in a lubricating oil or fuel to reduce the friction of an internal combustion engine in which the lubricating oil or fuel is used. An example of the alkoxylated hydrocarbyl amine compounds that are disclosed in this patent is N,N-bis(2-hydroxyethyl) oleylamine.
U.S Pat. No. 4,486,324 discloses an aqueous hydraulic fluid comprising at least 80% water and containing a hydrocarbyl-substituted succinic acid, a zinc dihydrocarbyl dithiophosphate, a hydroxyalkylamine, sodium alkyl benzene sulfonate, and optionally, a polyalkylene glycol mono-fatty acid ester.
U.S. Pat. No. 4,129,508 relates to lubricant and fuel compositions characterized by improved demulsifying properties. The patent discloses, for example, at Col. 12, lines 55 ff., an automatic transmission fluid which includes a number of additives including a dialkyl phosphite, the reaction product of a polyisobutenyl-substituted succinic anhydride, commercial tetraethylene pentamine, and boric acid prepared as set forth in U.S. Pat. No. 3,254,025, and a conventional friction modifier based on polyoxyethylene tallow amine (Ethomeen T/12), the reaction product of polyisobutenyl succinic anhydride and an ethylene polyamine, and Ethomeen C/15. The Ethomeen compounds are available commercially from the Armak Chemcial Division of Akzo Chemie.
U.S Pat. No. 2,151,300 relates to lubricating oil compositions which contain a major proportion of a mineral lubricating oil, a minor proportion of an organic phosphite, and a small amount, sufficient to bring about substantial stability of the phosphorous compound, of an oil soluble organic amine.
U.S. Pat. No. 4,634,543 relates to a fluid composition for use in a shock absorber. The fluid composition comprises a lubricating base oil, a boron-containing compound, and a dialkyl- or diaryl acid phosphate and/or a dialkyl- or diaryl hydrogen phosphite.
U.S. Pat. No. 3,645,886 relates to the concept of reducing or preventing the fouling of process equipment in petroleum or chemical industries wherein an organic feed stock is subjected to heat exchange at a temperature of from about 200.degree. to about 1300.degree. F., and there is added to that organic feed stock a mixture of a fatty acid ester of an alkanol amine and a mono-, di-, or triorganic phosphite ester.
U.S. Pat. No. 3,484,375 relates to the production of additives for lubricating oils, middle distillate fuels, residual fuels or reduced crudes in order to improve their resistance to oxidation, sludge formation, to improve their viscosity index, or to improve their flowability and pour point characteristics. The additives are prepared by reacting an organic phosphite ester containing at least one hydroxyl group attached to the phosphorous with alkaline polyamines or aminoalcohols.
U.S. Pat. No. 4,170,560 discloses additive compositions for use in crank case lubricating oils comprising a mixture of an oil soluble anti-oxidant and a oil soluble hydroxylamine which includes both Ethomeens and Ethoduomeens, which are trade names for compounds available commercially from the Armak Chemical Division of Akzo Chemie.
U S. Pat. No. 4,382,006 discloses a lubricating composition containing a friction reducing portion of a borated adduct of compounds which include Ethomeens.
U.S. Pat. No. 2,917,160 discloses the use of certain hydroxylated tertiary amines which include Ethomeen, as a corrosion inhibiting surface active lubricant for metal working. The amines may be used in the form of a salt. Phosphoric acid salts are illustrated.
U.S. Pat. No. 3,186,946 discloses cutting fluids in which the active lubricating component is a borate salt of a tertiary amine which includes both Ethomeen and Ethoduomeens.
U.S. Pat. No. 3,509,052 relates to lubricating compositions containing a lubricating oil, a dispersant which is a derivative of a substituted succinic acid, and a demulsifier. The demulsifier may comprise, for example, an Ethomeen, but the preferred demulsifiers are polyoxyalkylene polyols and derivatives thereof.
U.S. Pat. No. 3,502,677 relates to substituted polyamines which are useful as additives in lubricating compositions, fuels, hydrocarbon oils and power-transmitting fluids. The substituted polyamines are prepared by reacting an alkylene polyamine with a substantially hydrocarbon-substituted succinic acid-producing compound and a phosphorous acid-producing compound. The patent discloses the use of other additives in combination with the substituted polyamines wherein the other additives include phosphorous esters such as dihydrocarbon and trihydrocarbon phosphites. Other nitrogen- and phosphorous-containing succinic derivatives are disclosed in U.S. Pat. No. 3,513,093. The products disclosed in that patent are also useful as additives in lubricating oils, fuels, plastics, etc.
U.S. Pat. No. 4,557,845 discloses that the products of reaction between a 2-hydroxethyl alkylamine or certain higher oxylated members, and a dihydrocarbyl phosphite compound are effective friction modifiers and fuel reducing additives for internal combustion engines when such products are compounded with lubricants and liquid fuels. A similar disclosure is contained in U.S. Pat. No. 4,529,528, except that the products are prepared by reacting a bis(2-hydroxyethyl) alkylamine, a dihydrocarbyl phosphite and a boron compound.
U S Pat. No. 4,681,694 relates to a crankcase lubricating oil composition for slow speed diesel engines. The composition contains a mineral lubricating oil, an overbased calcium alkylphenolate, a zinc dihydrocarbyl dithiophosphate, an alkylated diphenylamine, and a rust-inhibiting amount of at least one dialkoxylated alkylpolyoxyalkyl primary amine.
U.S. Pat. No. 4,704,217 discloses a gasoline crankcase lubricant which contains a friction modifier having the formula: ##STR4## wherein R is a C.sub.1 -C.sub.20 hydrocarbyl radical, R' and R" are divalent C.sub.1 -C.sub.10 alkylene groups, a is an integer of about 1 to about 10 and x+y has a value of about 1 to 20.